Xylem 551-S Make-Up Water Feeder for Steam Separators and Receiver Tanks

The Xylem McDonnell & Miller 551-S is a float-operated make-up water feeder designed for applications where water is added to steam separators, receivers, feed tanks, and other vessels. This mechanical assembly uses proportional feed action to automatically maintain proper water levels in boiler systems without electrical switches or contacts.

Key Features:

• Proportional feed action for smooth, modulated water level control
• Quick-change replaceable cartridge valve and strainer for easy maintenance
• Float chamber connects via 1" NPT female equalizing pipe connections
• 3/4" FIP tapped inlet water connection
• Maximum water supply pressure: 75 PSI
• Maximum inlet water temperature: 120°F (49°C)
• Maximum vessel operating pressure: 25 PSI
• Compact design: 12-1/4" width x 10-3/8" height

The 551-S float is mechanically linked to the makeup control valve, which modulates open when water level drops and gradually closes as level rises. When the water reaches the center of the float chamber, the valve completely closes. This unit is commonly used on small, economical atmospheric feed tanks in commercial boiler systems. Optional float block accessory available for enhanced control.